1. Field of Invention
This invention relates to systems and methods desalinating seawater and, in particular, to low energy consuming systems and methods of desalinating seawater involving staged electrodialysis devices and electrodeionization devices having concentration-based potential half-cell pairs.
2. Discussion of Related Art
Sea water desalination was dominated by thermal processes such as vapor compression stills, multiflash distillation and others. Most thermal plants are located where there was abundance of power available for desalting sea water. Electrodialysis was typically used for desalting or desalinating brackish water. Reverse osmosis desalination systems are now more prominent because of such systems have lower power requirements and have lower capital and operating and maintenance costs, compared to thermal systems. The use of energy recovery devices in reverse osmosis systems has further reduced the energy consumption. However, reverse osmosis technology typically require at least about 2.5 kWh/m3. Thermal processes will continue to be high in power consumption due to phase change needed for desalination. If waste heat is available then processes such as membrane distillation may be used with power requirements of as low 1.5 kWh/m3.